Method of removing bark from logs



Feb. 22, 1944; M EDWARDS 2,342,533

METHOD OF REMOVING BARK FROM LOGS Original Filed July 4, 1939 3'Shee cs-Sheet l Feb. 22 1944. M EDWARDS 2,342,533

Feb. 22, 1944. w s 2,342,533

METHOD OF REMOVING BARK FROM LOGS Original Filed July 4, 1939 3 Sheets-Speak 3 MILES LON-ELL EDWARDS Patented Feb 22, 1944 METHOD OF REMOVING BARK FROM LOGS Miles Lowell Edwards, Longview, Wash, assignor to Weyerhaeuser Timber Company, Longview, Wash., a corporation of-Washington Continuation of application Serial No. 282,761,

July 4, 1939. This application January 21, 1942,.

Serial No. 427,619

- Claims. (or. 144-208) This invention relates to a new and novel method of removing the bark from logs, and has particular reference to a. method employing the use of a high velocity jet of water as the bark removing element.

In general, the bark of trees is important in the production of paper pulp only as it constitutes waste material which must be removed from logs which are to be converted into pulp. In each years growth of a tree there is added a soft formative tissue between the bark and the sap wood from. which new wood and bark originate. This formative tissue is known as the cambium. In the spring and summer months, because of tis viscid consistency, the soft cambium tissue permits the bark to be removed from the wood with move therewith a considerable quantity of wood,

with a consequent loss of much valuable material.

Experiments have been conducted over a period of several months duration in an endeavor to provide a commercially satisfactory method of removing the bark from logs hydraulically, and both winter and spring cut logs were used for test purposes. Round jets were first used, and exhaustive tests were conducted in. an effort to ,determine the angle at which a jet directed a relatively small amount of mechanical effort. A

Bark removed from trees cut during the spring and summer months is found to be relatively flexible and leaves the wood free from small pieces of bark and other objectionable fibers. In many instances, however, worms and other insects penetrate the outer bark to feed upon the inner bark, and, when this has occurred,'the injured bark is caused to cling tightly to the log. -It also frequently happens that injuries to the bark occur during logging operations, such as the removal make sure that small patches of inner bark are not left on the log. It appears, therefore, that although a great deal of the bark can be re- 7 moved from spring and summer cut logs much more easily than from fall and winter cut logs, the numerous places where the inner bark clings tightly to the log seem to require about the same pressure and flow of water for barking spring land summer logs as is required for barking winter ogs.

When the cambium tissue becomes dried out during the fall and winter months, it becomes tightly cemented to the wood of the tree. This is best understood when it is appreciated that from the cambium tissue is formed both the new annual ring of wood and the bark tissue outside of the wood. In the fall and winter months, the receding sap leaves the newly formed bark tissues hard and brittle, and each small particle of bark next to the wood clings tightly and must have direct application of force to be completely removed. Heretofore, this has been done by machines whlch cut the bark from the log and reagainst the surface of the log would remove the greatest amount of bark. These experiments developed that higher barking efilciencies were to be had with a plurality of round jets of very small diameter arranged in a plane perpendicular to the axis of the log and mounted in as closely spaced relation as nozzle structures would permit; and that each jet should be directed at an angle perpendicular to the surface of the log.

Even so, unclean areas were left between the cuts made by the individual jets. All of the outer bark was removed from the strip, but the inner bark was left on the log in strips for the full length of the log. Moreover, round jets are wasteful of both water and power, in that they direct too great a column of water against a given surface, and a very considerable proportion of the column does not perform useful work. Under the most optimum conditions, on the basis of performance or -barking efliciency, expressed in terms of kilowatt hours of electrical energy required to remove square feet of bark, all tests conducted with round nozzles proved that the method employed is unsatisfactory for commercial operations.

Conclusions from tests conducted over a period of several months duration have revealed that to effect commercially satisfactory operations for barking logs hydraulically, the water shouldbe delivered at the surface of the log in a solid, coherent, relatively thin and flat, high velocity jet, with the plane of the jet perpendicular to the longitudinal axis of the log and with the water striking the surface of the log at an angle of approximately ninety degrees. Full scale experiments have proven that thebarking efficiency of a jet of water is materially reduced if the angle of the jet is deviated as much as ten degrees to fifteen degrees from an angle perpendicular to the surface of the log. When water hits the log at an oblique angle a considerable proportion of the force of the jet, is reflected away from the log. The water bounces away from the place of impact with a force approaching that of the jet before striking the log. in the instant method the solid coherent stream of water striking the I log at a ninety degree'angle divides into two streams traveling axially in opposite directions towards the two' ends of the log. The peculiar type of erosion that occurs at the division of the stream at the place of impact has an important bearing on the success of the method. Provision is made forrelative longitudinal movement 'between the jet and the log whereby bark is removed in strips longitudinally of the log.

The present invention, therefore, is directed to a method of removing ,the bark from logs of mill run varieties regardless of the particular condition or characteristics of the bark or of the-logs. By the term logs of mill run varieaseasss dotted lines illustrating the reverse end posities is meant logs of the usual varieties as supplied to the mill from the woods, irrespective of the season of cutting, condition of bark, and nature of the logs as regards depressions, seams, limb stubs and otlier surface irregularities. The method does not require pretreatment of the logs such, for example, as by scoring or cutting the bark or by soaking the logs in hot water, but depends solely upon the action of a thin flat jet of water directed at the surface of the log in a-solid coherent stream and in a plane perpendicular to the axis of the log and at an angle of approximately ninety degrees to the surface of the log. Under the action of a high velocity jet of water of such description, the bark iscut from the surface of the log by a jet of water designed to obtain the greatest mechanical reactionthereagainst with a minimum expenditure of water horsepower. A particular advantage of the method herein described is the material saving in wood, it being estimated that this saving will amount to several millions of board feet annually for each installation e'mploying the method.

.Primarily, the object of the invention is to provide a method for removing the bark from logs to be used in the manufacture of wood pulp, solely by the action of a water jet which is formed in a particular manner and so directed .8

against the surface of the bark as to provide the wood free from bark.

It is a further object of the invention to provide a method of removing the bark from logs which is commercially feasible "for large scale installations, which effects a material saving of wood, and in which operating economies, reilected in labor saving and lower power costs, contribute materially to advantages enjoyed over methods'heretofore employed.

Still other. objects and advantages of the invention will be apparent to persons skilled in the art as the same becomes better understood by reference to the following detailed description, taken in connection with the accompanying drawings wherein is illustrated, somewhat diagrammatically, an equipment well adapted to carry out the method of removing bark from logs, it being understood that various changes in form, proportion, size and details of construction within the scope of the claims may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention.

In the drawings, Figure Tis a schematic elevation of a lay-out in which the method hereinafter described may be practiced mechanically,

parts shown in full lines illustrating the position of 'the nozzles at one end of the course through which they run, and parts shown in tion; Figure 2 is a fragmentary end elevationof the device illustrated in Figure 1, illustrating the log turning mechanism; Figure 3 is a sectional elevation of the traveling header and track therefor, showing the angle at which the jets are directed against the surface of the log; Figure 4 is an end view of one of the nozzles showing its outlet end; Figure 5 is a longitudinal section through the nozzle, taken on' the'line 5-5 of Figure 4; Figure 6 is a longitudinal section through the nozzle, taken on the line 66 of Figure 4, Figure 'l is a cross section through the nozzle, taken on the line 1--| of Figure 5; Figure 8 is a perspective view of the jet of water after leaving the nozzle, illustrating the changes in cross section of the jet from the time it leaves the outlet orifice of the nozzle until it impinges upon the surface of the log; and Figure 9 is a diagrammatic representation of an adaptation of the invention.

In general, the method embodied cants invention consists in creating one or more relatively thin and fiat, high velocity jets of water adapted to be directed against the surface of a log while supporting the log with its surface to be impacted by the jet in a plane normal to the plane of the'jet, with the plane of the jet substantially perpendicular to the axisof the log, and creating a relative movement between the log and the jet whereby a strip of bark the full length of the log is subjected to the action of the jet. This may be done either by providing longitudinal movement to travel longitudinally of the log, the log being supported in close proximity to the path of travel of the jets in such manner as to compensate for the natural taper of the log. The

path of travel of the jet is intended to be parallel with that portion of the surface of the 10% which is being acted upon by the jet. By so adjusting the position of the log, a jet of water projected from a nozzle moving in a fixed plane will be delivered at the surface of the log with the least possible variation in the length of the jet during the cutting stroke.

An important feature of applicant's method l0 resides in the steps of providing a jet of water which forms a thin and flat, knife-like cutting edge, and directing the jet against the surface of the log with the plane of the cutting edge substantially perpendicular to the longitudinal axis of the log. The jet of water is-directed at the surface of the log from an angle of ninety degrees with respect to the point on the surface impinged by the jet, whereby the full force of the jet is utilized at the place of impact. The problem is one of erosion, the solution thereto having heretofore been sought in the provision of rossing machines and othersimllar devices for scraping, chipping, or scouring the bark from the solid wood of the log. Relative-movement between the jets of water and the log may be accomplished either by providing longitudinal and rotative movement to the log, in which case the longitudinal movement of the log may be between intermittent rotative movements of the log, or by causing the jets of water to move from end to end of the log between intermittent rotative movements of the log, as in the manner herein illustrated and described.

An equipment adapted to carry out the above described method comprises a source of water in applisupply, herein illustrated as a supply pipe I, the

' flow of water therefrom being under control of a valve 2, from which water is supplied to a stationary or fixed header 3. From the fixed header 3 the water is conducted through flexible conduits I to a traveling header 5, the conduits 4 being trained around traveling sheaves 5 which are maintained the distance apart permitted by the loops of the conduits 4 by cables 'I trained around fixed sheaves 88. The traveling sheaves 5 are mounted in blocks Sadapted to be moved along a rail to provide for-the movement of the traveling header 5. Movement of the traveling sheaves is under control of cables I I through which motion may be transmitted to the blocks 9 from any suitable source, not shown. The traveling header 5 is mounted upon a carriage l2 equipped with wheels l3 which engage vertically aligned rails ID, the uppermost of which forms the track for the blocks 9-9. The water is projected from the traveling header 5 in the form of wedge-shaped jets by means of nozzles l4, presently to, be more specifically described, one ormore of which may be employed as may be desired. Where more than one nozzle is employed, each is so mounted with respect to the others that the jets of water projected thereby are delivered in edge to edge relation to produce the effect of a single wide sheet of water. In this manner, whether or not the jets of water are in alignment transversely of the log, they coact to redegrees, while the bores converge at an angle of approximately fifteen degrees between center lines'of the respective bores, as indicated by the angle 'a in Figure 6. The center lines of the bores intersect with the axis of the nozzle ,at a point b located at a distance from the end of the nozzle substantially equal to the length of the short axis of the oval orifice. This distance is not critical but may vary somewhat depending upon the angle of taper of the two bores and the angular relation of their center lines. The distance must be finite, however, in order to impart an oval shape to the orifice, it being -understood that if it were zero, the orifice would be circular in cross sectional shape. With bores Y of the taper and angular relation stated above,

the total width of the several jets.

The drawings illustrate the log carriage l5 as being mounted upon independently actuated hydraulic lifts l6, one of which is positioned at each end of the log carriage, by means of which the log I! may be supported in close proximity to the Path of travel ofthe header 5 along the rails It. By reason of the flexible adjustment of the log carriage l5 permitted by the hydraulic lifts IS, the full length of the upper surface of the log (which is that portion of the surface of the log to be acted upon by the jets) may be brought into a plane approximately parallel with the rails l0. Thus the distance between the nozzles I! and the surface of the log to be impacted by the jets does not vary greatly -throughout the path of travel of the nozzles above the log, excepting for such abrupt changes in this measurement as may result from natural causes other than the normal taper of the log.

The carriage I5 is equipped with a cradle consisting of idler rollers l8 and driven rollers IS, the latter of which is driven by suitable mechanism, indicated at 20, to provide an intermittent rotative movement to the log m timed relation to the travel of the traveling header 5. I

The structure of the nozzles I4 is more clearly shown in Figures 4 to 7, inclusive, and comprises a fluid delivery passage 2| which, in general, is oval in cross section, and which is caable of forming a thin, fiat jet for producing an eificient, substantially continuous cutting edge upon a work surface spaced a relatively great distance from the nozzle orifice. In thi instance the fluid passage of the nozzle is formed by the convergence of conjoined or overlapping bores, each of which corresponds in shape to the frustum of a simple circular cone, and so decreases in cross sectional area uniformly throughout the length of the nozzle. In the particular constructionof the nozzle illustrated, the bores have a taper of approximately five nozzle main fiuid channel.

the point b of intersection of the center lines is spaced from the end of the nozzle a distance approximately equal to the length-of the short axis of the oval orifice 22 in the end of the nozzle. It will be observed that the apices of the extended surfaces of the two tapered bores, indicated at 0, lie farther from the end of the nozzle than the point D. This is due to the fact that the passage is of decreasing eccentricity from the inlet to the outlet, the eccentricityv or overlap of the bores at the inlet end, as illustrated in Figure 7, being of the order of fifty percent. It will be obvious that the amount of overlap of the tapered bores at the inlet end may be reduced to that occurring at the outlet end and hence be constant throughout the length of the nozzle passage. In this instance the eccentricity of the passage cross section will be constant and everywhere correspond with that of the orifice, and points h. and 0 will be common although spaced from the end of the While in the construction shown the passageway is not, in a strict sense, oval shaped in cross section throughout its length, due to slight longitudinal ridges at the intersection of the tapered bore surfaces, however, the presence of these ridges has substantially no effect in the formation of the jets, particularly since they practically disappear at the orifice end.

The mouth of the nozzle is reamed so as to provide a smooth conical approach to the passageway as indicated at 2|. The outer diameter of the conical reamed portion corresponds substantially to the maximum cross sectional dimensionof the oval passageway, but the taper thereof is much greater than the bores forming the. For all practical purposes, therefore. the fluid passage 2| may be considered to be generally oval in cross section throughout its principal length, and to be progressively decreasing in cross sectional area.

In Figure 8 is shown the character of the stream projected by each nozzle. The stream issuing from the orifice 22 is in the form of a solid body of liquid slightly oval in cross section. Upon advancing away from the nozzle the stream develops into a fiat. uniform, coherent sheet of water, the plane of which is at right angles tothe long axis of the oval shaped nozzle orifice. Preferably, the jets of water are projected a distance of from fifteen to twenty inches, at which distance each jet is delivered at the surface of the log in an intact stream having a thin cutting edge of the order of four inches in width. In a commercial installation it has proven to be sound economy to project the jet of water under a pressure of 1200 pounds per square inch, which is suflicient to create an eroding or scouring action at the surface of the log adequate to remove thereto.

' patch of bark the bark without injury to the. wood. For reasons hereinbefore mentioned, when extreme cleanliness is required, it has been found that the removal of bark from'spring cut logs requires approximately .the same application of ppwer as does the removal of bark from winter cut logs.

In operation,- an unbarked log is placed upon the log carriage l5 and the .lifts I. manipulated to so position the log that the surface of the log is parallel with the path of travel of the traveling header 5. The log is supported with the surface to be impacted by the jets at a distance of from fifteen to twenty inches from the outlet orifice of the nozzle. By manipulation of the cable ll through which motion is transmitted to the traveling sheaves i, the traveling header 5 is caused to move longitudinally of the log for a distance greater than the length of the log. This is to cause the nozzles i4 and the jets of water projected thereby to run t course which will carry them beyond the ends of the log before their direction of travel is reversed. 'The reasons for this procedure are two-fold, one being to insure that the bark is removed from the full length of the log. and the other being to avoid brooming the ends of the log by bringing the jets to a stop thereover.

Figure 9 illustrates diagrammatically the application of a method of removing bark from logs employing a thin flat jet directed against the surface of the log at right angles with respect The drawings illustrate a log of the mostcommon type and having portions of limbs projecting outwardly through the bark layer. A portion of a log 23 is shown having a bark layer .24, shown in section, and stubs 25 and 25 of limbs projecting outwardly from the wood through the bark layer. A log is shown which is being cleaned of bark by a flat jet 29 ofwater directed against the surface of the log at right angles with respect thereto in a manner according to the instant invention. As the limb stub 25 passes under the jet no portions of the bark layer are shielded thereby from the force of. the jet. As a consequence, the bark is removed from the log around all sides of the limb projection.

It will be noted thatthe perpendicularly arranged jet 2! expends itsforce at the surface of the log in two opposite directions on both sides of the plane of the jet, as indicated by the reflected jet portions 32 and 33. As regards loosely adhering bark portions, the forwardly reflected I jet portion 33 acts with a wedging-action under the forward edge of the bark layer II to pry it loose from the surface of the log. In the event that the bark layer is firmly adherent, then the forward edge of the bark layer will be sheared by the thin flat jet is much in the manner of a cutting knife. Since the outer portion of the bark layer is always relatively soft, it is readily sheared through by the flat jet. The cambium layer of the bark also is sheared from the 8111': face of the log in very small portions. Assume, however, that a portion of the cambium. bark passes under the jet 2! which is firmly adherent at a point to the surface of the log. This point of the cambium layer may not be detached from the log surface by action of the forward jet portion 33, with the result that a smallisland of bark may pass the plane of the jet 29. Upon passing of the plane of 34 is subjected to the rearwardly reflected portion 32 of the jet and hence to a force in the opposite direction to which it was initiallysubjected. The rear edge of the patch the main jet, the small=v aseasss is lifted 'up by the jet portion 32 and is torn from the log surface. In passing under the force of the main jet the patch 34 is consid' erably loosened from the log surface, whereby its removal is facilitated by the action of the secondary jet portion 32.

Having now described my invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

1. A method of applying a stream of water to the surface of a log so as to effect substantially complete removal therefrom by erosion of unscored uncut bark, consisting of combining a plurality of high velocity, radially directed, thin and flat jets of water in edge-to-edge relation to" produce a flat stream of greater width than a single jet and having the direction of greatest width of said flat stream disposed transversely to the longitudinal axis of the log, supporting the log with its surface to be impacted by the jets in a plane normal to the plane of the jets, and

- moving the jets along a predetermined pathway longitudinally parallel to the surface of the log.

2. The method of removing bark from run varieties of logs which consists in supporting I a log with a longitudinal portion of its surface exposed to a jet of water, forming a jet of water so as to have a thin and flat configuration where it strikes the surface of the log, directing said jet against the surface of the log with the cutting edge of the jet in a plane transversely to the longitudinal axis of the log and at an angle of approximately 90 degrees to the surface of k the log, creating a relative longitudinal movement between said jet and said log, and effecting substantially complete removal of the bark from said log solely by the action of the jet.

3. The method of removing bark from mill run varieties of logs which consists in supporting the log with a longitudinal portion of its surface exposed to one or more jets of water,

forming the jets of water so as tohave a rela-' tively thin and flat configuration where it strikes the surface of the log, moving the jets of water along a predetermined pathway longitudinally parallel with the exposed surface portion of the log, applying each jet of water to the expowd surface of the log'with the cutting edge of the jet in a plane transverse and substantiallyperpendicular to the longitudinal axis of the lo and at a velocity sufficient to cut through and substantially completely remove the bark from the log, turning the log ,to expose successively all of its surface to the action of the jets, and effecting substantially complete removal of vthe bark from said log solely by the action of said jets.

4. The method of removing bark from logs I consisting of supporting a log with a longitudinal portion of its surface exposed to a jet of water, forming a relatively thin and flat high velocity jet of water having a chisel-like edge, moving said jet of water longitudinally of a log, directing said jet of water against the surface of the log in a solid coherent stream with the plane of the jet substantially perpendicular to the surface of the log and with the greatest width of said jet disposed transversely to the longitudinal axis of the log, applying said jet to the exposed surface of the log at a velocity suilicient to substantally remove the bark therefrom, each movement of said jet of water being to a point beyond the end of the log, turning the log. and reversin the movement of said let of water.

5. The method of removing bark from logs comprising supporting a log with a longitudinal portion of itssurface exposed to a jet of water, forming a jet of water having a. thin and flat cutting edge where it strikes the surface of the log, directing said jet against the surface of the log in a solid coherent stream with the cutting edge of the jet in a plane substantially perpendicular to the surface of the log and 5 with the greatest width of the jet disposed transversely to the longitudinal axis of the log, and creating a relative longitudinal movement between said jet and the log while applying said jet to the exposed surface. of the log at a velicity' suflicient to substantially remove the barkv therefrom by the action-ofthe jet.

' MILES LOWELL EDWARDS. 

